Of all the activated supports I've identified for peptide/protein
immobilization for affinity chromatography, Eupergit best meets my 3
selection criteria - security of supply; ease of use; batch-to-batch
reproducibility.  I've also considered resins from
Pharmacia/Amersham(now GE health systems); Pierce; Biorad; Toso; 3M's
Azlactone beads; TESSEK Separon Epoxy activated gels.  Have I missed
any alternatives to Eupergit?

My chief hesitation about Eupergit will have to be answered
empirically, and  it concerns steric hindrance effects. My immobilized
ligand is about 19kD and my target is about 62kD. I'm concerned that
with no spacer arm on the Eupergit bead, and direct attachment of my
ligand to the bead, there may be steric hindrance problems which will
materially affect dynamic binding capacity of my target.  The target
to be bound is a 62kD protein in porcine whole blood. For reasons I
cannot disclose here, I want to be able to add the Eupergit as
commercially supplied, without modification, directly into the
solution containing my 17kD ligand which is to be immobilized on the
bead.  Your comments regarding likely steric hindrance, or other
problems?

Because the solution from which I need to purify/deplete/extract my
target is whole porcine blood, proteolytic cleavage will be a factor,
but that would be the case with any support/ligand alternative I might
choose.  I will have to determine leakage of ligand from the gel. 
Your thoughts on non-proteolytic leakage of the ligand based on the
Eupergit attachment chemistry alone ?

I may modify my process so that my target is in porcine plasma, so
that I might operate in a column mode, rather than a stirred batch
mode, as necessitated when processing whole porcine blood.  Any
experience using Eupergit to process plasma?